1. Field of the Invention
The present invention relates to a process for producing a membrane for an electrolysis. More particularly, it relates to a process for producing a membrane suitable for an electrolysis of water or an aqueous solution such as an aqueous solution of an acid or a base, an alkali metal halide or an alkali metal carbonate.
2. Description of the Prior Art
In an electrolysis of said aqueous solution especially, a process for producing an alkali metal hydroxide and chlorine by an electrolysis of an aqueous solution of an alkali metal chloride, a diaphragm or membrane process has been employed instead of a mercury process in view of the prevention of public pollution. In the diaphragm or membrane process, an asbestos liquid permeable diaphragm has been mainly used as a diaphragm for partitioning an anode compartment and a cathode compartment in an industrial operation. The diaphragm has been usually formed by depositing asbestos fiber on a perforated metallic cathode. On the other hand, an electrolysis using a liquid impermeable membrane made of an ion exchange material has been proposed to overcome the disadvantages of the electrolysis using the liquid permeable diaphragm. The liquid permeable membrane made of an ion exchange material i.e. an ion exchange membrane is usually supplied in a form of a film. Therefore, it could not be used for the purpose of direct deposition on the perforated metallic cathode. The following process has been proposed as a process for directly forming a liquid impermeable ion exchange membrane on the conventional perforated metallic cathode as disclosed in Japanese Unexamined Patent Publication No. 142,678/1977: An asbestos layer is formed on a surface of a perforated electrode and then, a thermoplastic ion exchange material layer is deposited and is melt-bonded on the surface of the asbestos layer by a heat treatment to convert it into a water impermeable membrane whereby a membrane of a melt-bonded asbestos ion exchange material layer is formed on the perforated cathode. Thus, the conventional diaphragm electrolytic cell is converted into an ion exchange membrane type electrolytic cell. According to said process, it has been difficult to overcome the disadvantages of trouble caused by the incorporation of an asbestos layer in the membrane and the requirement of a high temperature such as 240.degree. to 300.degree. C. in the melt-bonding step.